DE2712947A1 - PROCESS AND EQUIPMENT FOR FLOTATIONAL SEPARATION OF SOLID CONTAMINATION FROM A LIQUID - Google Patents

Description

SWEMAC, SOCIETE ANONYME

Subject of registration: Procedure and device for

Flotation separation of solid contaminants from a liquid

709842/0702

The present invention relates to a method of rotary deposition of impurities that are contained in a liquid in the form of solid particles. According to this procedure a stream of air is injected into a certain amount of the liquid to be treated in a flotation cell, in such a way that Air bubbles form that are dispersed in the liquid, attach to the contaminant particles, and then back to the surface rise; in this way they create a foam that goes with this. Impurities is accumulated and that of the surface this liquid is withdrawn.

There is a flotation process of the type described above for removal of printing inks from paper pulp made from waste paper. In this process, air is fed directly into the Cell floor by suction with a propeller that also ensures thorough mixing and distribution of the fibrous suspension in this cell.

The direct air supply into the paper pulp allows, without a doubt, a regulation of the air pressure and thus also the diameter of the Air bubbles depending on the air volume, which in turn can be regulated within certain limits. Even if by an increase of the air volume, the air pressure and consequently the diameter of the air bubbles can be increased, it is nevertheless after this known methods impossible to reduce the diameter of the air bubbles and still increase the amount of air supplied, which may be necessary in certain cases in order to cause the separation of certain impurities.

It has been found that it was possible, to a surprising degree, to achieve a selective separation of the impurities Achieve flotation by independently controlling the size of the air bubbles and the volume of air. In this way is it z. B. in the removal of printing ink from defibered, pretreated and made from waste paper pulp now possible to generate different air bubble sizes depending on whether it is the flotation of printing inks or impurities such as kaolin or fibers, whereby a selective separation of these substances is effected.

709842/0702 " ³ ~

The present invention relates in particular to a method which allows the air bubble sizes to be regulated independently of the volume of air that is added to the liquid to be cleaned became.

For this purpose, according to the invention, before the air and liquid are injected into the flotation cell, at least one Mixing chamber circulate this liquid in the form of a thin film, with the air at the same time and transversely to the orbit of the Liquid and is fed to part of this orbit.

It was also found that when the liquid is a fiber suspension such as paper pulp, the forcible introduction of the pulp in the form of a thin film into a narrow one Chamber as well as their impact on the divided and perpendicular to the A thin film of liquid injected with suspended fibers has a friction and cleaning effect exercises these fibers.

A feature of the method according to the invention is that the thickness of the liquid film in the chamber and consequently also the rate of introduction of the liquid into this chamber is regulated.

During the removal of printing ink from waste paper pulp, it was found that the volume of air added to the pulp and the rate of introduction the mass in the mixing chamber have an influence on the degree of bleaching of the mass; become these sizes regulated, you can achieve graded degrees of bleaching from 57 ° to 66.50 ° scan.

These settings allow effective cleaning with a minimum of residue.

According to a further method feature, the length of the air flow supplied to the liquid to be treated is regulated.

In this way, the amount of air can be precisely dosed in relation to the liquid film passing through the mixing chamber.

709842/0702

-Jr--

Another process feature is that the foam through a stream of air is entrained into a funnel and the air is recovered for reuse.

In the case of flotation with multiple cells, a mixture is created in each cell introduced from air and liquid, each coming from one of the mixing chambers. In this way, the Regulate air bubble sizes differently from cell to cell and selectively separate the impurities.

If the liquid contains fibers, one can - avoid major fiber losses to avoid - reintroduce the foam from the remaining cells into the liquid to be cleaned, and that into the first Flotation cell is passed.

The present invention also relates to a device for applying the method.

According to the invention, this device also includes at least one a narrow mixing chamber upstream of the flotation cell, through which a thin film of the liquid to be purified flows can and which is equipped with a device which the air flow perpendicular to the thin introduced into the chamber Liquid film supplies.

One feature is that the mixing chamber is separated by two parallel walls is limited, which are arranged at a distance from each other that the liquid film to be cleaned is passed through can be.

According to a further feature, the mixing chamber has a distance regulator between the two parallel walls.

Further features and details of the invention are evident from the description of such a device with reference to the drawings attached to this document. This document is merely an example of an embodiment of the invention, which is primarily used for the deposition of printing ink Paper pulp based on waste paper is suitable.

Figure 1 is a schematic longitudinal view of a device

709842/0702

with several floors;

Figure 2 is the horizontal section along line II-II of Figure 1;

Figure 3 shows, on an enlarged scale, a view of a longitudinal section through a mixing chamber ;

Figure 4 is a sectional view along the line IV-IV of Figure 3;

- Figure 5 shows, on an enlarged scale, the vertical section through a first embodiment of a mixing chamber:

Figure 6 is a sectional view taken along line VI-VI of Figure 5; and

- Figure 7 is a graph of the bleaching curves.

The components in these illustrations have the same identification numbers.

The device includes four flotation cells 1, 2, 3, 4. These cells are ring-shaped and placed axially one above the other so that they form the four floors of a tower with several floors (5). Of course, this tower could also have more or less than four floors.

The defibered and chemically pretreated paper pulp, which is in the form of a fibrous suspension with a foaming agent, is fed with the help of a pump (6) through a line (7) to the inlet of cell (1), after it first enters a mixing chamber (8) has gone through. This chamber consists of a narrow passage where the fibrous suspension circulates in the form of a thin film, at the same time air is supplied perpendicular to the flow direction of this paper pulp film or along a corresponding section through line (9); Line (9) is connected to a compressed air source (not shown) with the interposition of a cock (10).

709842/0702 - ⁶ -

g (λ \) it

The mixing chamber (8) is connected to the ring-shaped cell (1) by a line (λ \); Line (11) opens tangentially into the cylindrical wall of the cell near its bottom (5) ei: so that a rotary movement of the fibrous suspension is effected around the centrally arranged channel (12) of the annular cell. The air bubbles generated in the suspension attach themselves to the impurities and transport them to the surface in the form of foam. The foam is withdrawn from the cell via outlet (18) and partly through the rotary movement of the suspension and partly through an air flow generated above it into the channel (12). A vertical plate (50), which is arranged above the fill level of the paper pulp, directs the foam to the outlet. The foam is collected in a funnel (13) enclosed by the channel (12); then the foam arrives in a residue container (37) filled with water. The air flow used to draw off the foam is supplied to the upper cell section through conduit (14) which is connected to a suction device (15); this device is located above an axially arranged, conically tapering tube (16) which is used to recover the air for drawing off the foam. This pipe is mounted concentrically in the central foam discharge duct (12) and serves all cells placed one above the other. The air used for extracting the foam is introduced into the cell through the opening (17) and leaves it through the outlet (18), entraining the foam, which falls under the force of gravity into the funnel (13), while the air passes through the pipe (16 ) escapes. This pipe extends into the neighboring cell (2) and forms a cone that narrows towards the top and is arranged concentrically opposite the wider pipe, through which the air is recovered, which is released from the foam from this neighboring cell and from the other cells (3 , 4) serves. The components of the pipe (16) form a cyclone which, due to its shape, accelerates the foam in a centrifugal manner and thus separates it from the air which is sucked into this pipe under the action of the suction device (15). From there, the air is fed back into the line (14) and used again to remove the foam.

The paper pulp, which has been partially cleaned in cell (1), exits via line (19) into which a pressure pump (20) is switched on The line (19) extends into the mixing chamber of the next one

709842/0702

- 7th

J ₄ 27129A7

Cell (4) in, which is on the last floor of the tower; the process here is identical to that in the first Cell or in the subsequent cells.

The paper pulp or the water, which contains increasingly cleaner fibers, is fed into these cells one after the other, while the foam collected in the other cells is in turn put back into the bottom cell.

The foam, which contains the residues from the first cell and from the remaining cells, can of course either be reused or deducted on each floor for treatment in a separate facility according to the type of product for which the mass is provided.

The device also includes a cover (40) which closes the cell on the last floor; a control window (41) that can be removed quickly for cleaning; a drain valve (42) for each cell; a valve (46) in the air line for the Peeling off the foam; a base (43) in the tube (12) for receiving the re-used residues; a line (44) for the withdrawal of this Residues in cell (1) and a line (45) for withdrawing the mass from cell (2), where the most purified mass is treated will.

Figures 3 and 4 or 5 and 6 each represent two versions shape the mixing chamber.

In the embodiment according to Figures 3 and 4, the mixing chamber has one rectangular cross-section and two straight, parallel ones Walls (21, 22) which are mounted in a cuboid body (23) and a connecting channel with the supply line (7) and the outlet line (11) for the mass. The wall (21) can be displaced parallel to the wall (22) and is actuated by a thread shaft (24) which is guided in a threaded hole (26); this hole leads through a Sleeve (27) which is embedded in the upper wall adjacent to the cuboid body. This is made possible by the Control (25) a distance control between the parallel

709842/0702 - ⁸ -

walls and thus the definition of the thickness of the paper pulp film, exposed to the air flow. The wall (21) is provided with a membrane for sealing the chamber, whereas the wall (22) consists of a porous material, such as glass frit, which directs the air flow to the through the chamber Lets pass paper mass film. It is advantageous if the mixing chamber is also provided with a plate (28) is, with which one can seal part of the passage area which is provided in the plate of glass frit; this allows c Air flow rate can be regulated.

According to the embodiment in FIGS. 5 and 6, the mixing chamber (8) has a conical shape and has two conical parallel walls (29, 30) which are arranged so far apart that they form a passage for the paper pulp. The paper pulp is fed into the chamber through a nozzle (31) which opens tangentially through wall (29) into the chamber and thus applies a rotary movement to the paper pulp, while the air jet hits the pulp through channels (47) in the inner wall (30) hits; these channels are connected to an air inlet opening (32) which is connected to a compressed air source (not shown). The inner cone (30) is axially displaceable in the outer cone (29) so that the distance between these walls and thus also the thickness of the paper pulp film can be changed. In order to achieve this, the rotatable, inner cone is controlled by a tube (32) which at the same time represents the air supply line. A conical sealing device (33), which is mounted inside the cone (30), namely on two shafts which can be displaced in the end walls of the cone (30), allows part of the openings in the air distribution cone to be sealed, which changes the area through which air enters the mixing chamber. By regula independent of the rotational speed of the pulp and of the feed rate of the mass of air access an air bubble size is generated in the cells, which is suitable in each case for the flotation of inks, of kaolin or of fibers and thus causes a selective deposition of these constituents.

The invention described relates to a device for

709842/0702 - 9 -

Separation of printing ink from paper pulp. However, it can also be used in other areas, such as washing of minerals or for the purification of lead water by flotation of the fibers. Based on laboratory tests, it was possible that Create diagram according to Figure 7; here are the bleaching curves (48 and 49) of the paper pulp as a function of the ratio between the air volume / paper mass volume and the speed of the mass in the mixing chamber. On the The abscissa is the ratio of liters / air to liters / paper pulp and the ordinate is the degree of bleaching of the paper pulp in Degree scan indicated. The curve (48) corresponds to a paper pulp bleaching at a mass speed of 4.23 m / sec, while curve (49) shows a degree of bleaching at a pulp speed of 6.35 m / sec.

By changing the ratio between the Gemisdi air / paper pulp and the speed of the paper pulp in the mixing chamber, bleaching differences of 57 to 66.5 ° can be achieved. The experiments were ⁿ magazine paper "is carried out with waste paper of the type containing about 50% of mechanical pulp, the original degree of bleaching corresponds to the unprinted edges of 66.5 Scan °

Using the method according to the invention, the bleaching of the printed parts, which contain about 2 % printing ink, can be improved from 46 to 66.5 scans after a dwell time of 20 minutes. After a dwell time of 2.5 minutes, the degree of bleaching improves from 46 ° scan to 64.5 ° scan.

The best conventional method to date has a scan of 62.3 ° or after 2.5 ° with the same paper after a dwell time of 20 minutes Minutes about 54 ° scan performed.

It is obvious that this invention is not limited exclusively to the illustrated embodiments, but that many modifications in the shape, arrangement and nature of certain components required for construction are possible without departing from the concept of the present invention . This applies provided that these modifications

709842/0702

- 10 -

are not in contradiction to the following patent claims.

- 11 -709842/0702

Blank page

Claims (21)

PATENT CLAIMS 1. Process for the flotation separation of impurities that are contained as solid particles in a liquid. To In this process, an air stream is fed into a certain amount of this liquid to be treated in a flotation cell injected in such a way that air bubbles form, which are distributed in the liquid, attach themselves to the impurities and rise again to the surface; this creates foam. which is enriched with these impurities and is drawn off from the surface of the said liquid. The procedure is characterized in that before the air and the liquid are injected into the flotation cell, this liquid is brought into circulation in at least one mixing chamber in the form of a thin liquid film, with air at the same time perpendicular to the orbit of this liquid and along a portion of this path. 2. The method according to claim 1, characterized in that the thickness of the liquid film in the mixing chamber is regulated « 3. The method according to any one of claims 1 and 2, characterized in that regulating the length of the section on which air is injected into the liquid to be treated. 4. The method according to claim 1, characterized in that a stream of air is passed into the flotation cell ₍ at the level of the foam, whereby it is carried away and falls into a funnel, while the air is recovered for reuse. 5. A method of separating impurities according to any one of claims 1 to 4 - flotation with a plurality of flotation cells characterized in that a mixture of liquid and air coming from a mixing chamber is fed into each cell. 6. The method according to claim 5 _f, characterized in that the foam is drawn from the flotation cells into a common funnel, while the air used for this drawing is drawn in to use it again. ? 09842/0702 _ _ ORIGINAL INSPECTED 7. The method according to any one of claims 5 and 6, characterized in that that the foam originating from the remaining cells is used again in the liquid which is in the first flotation cell is directed. 8. Device for the flotation separation of impurities which are contained in a liquid in the form of solid particles are, wherein this liquid contains at least one foaming agent. The facility includes at least one flotation cell; through which a certain amount of this liquid to be cleaned and a stream of air are passed, so that a flotation foam as a result, the air bubbles attach to the contamination staple. The device is further characterized in that it also has at least one narrow cell upstream of the flotation cell Has mixing chamber that can let through a thin film of the liquid to be cleaned and with a device through which the air flow can be injected into the chamber perpendicular to the liquid film. Device according to Claim 8, characterized in that the mixing chamber is delimited by two parallel walls, the are arranged at such a distance from one another that the liquid film to be cleaned is passed through. 10. Device according to claim 9 »characterized in that the two walls of the mixing chamber are conical and the inner wall is rotatable. 11. Device according to one of claims 9 and 10, characterized in that that the mixing chamber is provided with a device by which the distance between the two parallel walls can be regulated. 12. Device according to one of claims 8 to 11, characterized in that that the mixing chamber is equipped with a device through which the air passage area to the chamber can be regulated. 13. Device according to one of claims 8 to 12, characterized in that d ^ 2 the mixing chamber with the cylindrical flotatioi cell is connected by a line that runs along its side 709 8% 2/0702 - 13 - opens near the ground. 14. Device according to claim 13, characterized in that the end of the line which connects the mixing chamber with the cell opens tangentially into this. 15. Device according to claim 8, characterized in that the flotation cell has an air inlet opening in the upper section through which the foam is withdrawn from this cell. 16. The device according to claim 15, characterized in that the Flotation cell is annular and defines a centrally located channel surrounding a funnel; in this funnel will the foam is drawn off and collected by the air flow. 17. Device according to claim 16, characterized in that an axially arranged recovery pipe for the foam exhaust air is provided in the central channel above the funnel. 18. Device for flotation by battery-shaped cells, characterized in that several axially superimposed on it Cells belong, in accordance with any preceding claim, and for several Cells having communal foam vent lines. 19. Device according to claim 18, characterized in that the lowermost flotation cell is mainly used to treat the cleaning fluid is reserved, while in the remaining cells one after the other the increasingly more purified fluid is abandoned, the foam withdrawn from these remaining cells being reinserted into the bottom cell. 20. Device according to one of claims 18 and 19, characterized in that that to her an axially arranged and all cells common recovery pipe for the foam exhaust air heard. 21. Device according to one of claims 18 to 20, characterized in that that the recovery pipe for the foam exhaust air 709842/0702 - 14 - protrudes from the bottom cell into the neighboring cell and towards the top forms a narrowing cone, which is arranged opposite the wider tube through which the foam exhaust air is recovered from this neighboring cell as well as from the remaining cells. 709842/0702 - 15 -